Implantable neurostimulation systems have proven therapeutic in a wide variety of diseases and disorders. Pacemakers and Implantable Cardiac Defibrillators (ICDs) have proven highly effective in the treatment of a number of cardiac conditions (e.g., arrhythmias). Spinal Cord Stimulation (SCS) systems have long been accepted as a therapeutic modality for the treatment of chronic pain syndromes, and the application of tissue stimulation has begun to expand to additional applications such as angina pectoralis and incontinence. Deep Brain Stimulation (DBS) has also been applied therapeutically for well over a decade for the treatment of refractory chronic pain syndromes, and DBS has also recently been applied in additional areas such as movement disorders and epilepsy. Further, in recent investigations Peripheral Nerve Stimulation (PNS) systems have demonstrated efficacy in the treatment of chronic pain syndromes and incontinence, and a number of additional applications are currently under investigation. Also, Functional Electrical Stimulation (FES) systems have been applied to restore some functionality to paralyzed extremities in spinal cord injury patients.
These implantable neurostimulation systems typically include one or more electrode carrying neurostimulation leads, which are implanted at the desired stimulation site, and a neurostimulator (e.g., an implantable pulse generator (IPG)) implanted remotely from the stimulation site, but coupled either directly to the neurostimulation lead(s) or indirectly to the neurostimulation lead(s) via a lead extension. Thus, electrical pulses can be delivered from the neurostimulator to the neurostimulation leads to stimulate the tissue and provide the desired efficacious therapy to the patient. The neurostimulation system may further comprise a handheld patient programmer in the form of a remote control (RC) to remotely instruct the neurostimulator to generate electrical stimulation pulses in accordance with selected stimulation parameters. The RC may, itself, be programmed by a clinician, for example, by using a clinician's programmer (CP), which typically includes a general purpose computer, such as a laptop, with a programming software package installed thereon.
In the context of an SCS procedure, one or more neurostimulation leads are introduced through the patient's back into the epidural space, such that the electrodes carried by the leads are arranged in a desired pattern and spacing to create an electrode array. Multi-lead configurations have been increasingly used in electrical stimulation applications. In the neurostimulation application of SCS, the use of multiple leads increases the stimulation area and penetration depth (therefore coverage), as well as enables more combinations of anodic and cathodic electrodes for stimulation, such as transverse multipolar (bipolar, tripolar, or quadra-polar) stimulation, in addition to any longitudinal single lead configuration. After proper placement of the neurostimulation leads at the target area of the spinal cord, the leads are anchored in place at an exit site to prevent movement of the neurostimulation leads.
To facilitate the location of the neurostimulator away from the exit point of the neurostimulation leads, lead extensions are sometimes used. The neurostimulation leads, or the lead extensions, are then connected to the IPG, which can then be operated to generate electrical pulses that are delivered, through the electrodes, to the targeted tissue, and in particular, the dorsal column and dorsal root fibers within the spinal cord. The stimulation creates the sensation known as paresthesia, which can be characterized as an alternative sensation that replaces the pain signals sensed by the patient.
The efficacy of SCS is related to the ability to stimulate the spinal cord tissue corresponding to evoked paresthesia in the region of the body where the patient experiences pain. Thus, the working clinical paradigm is that achievement of an effective result from SCS depends on the neurostimulation lead(s) being placed in a location (both longitudinal and lateral) relative to the spinal tissue, such that the electrical stimulation will induce paresthesia located in approximately the same place in the patient's body as the pain (i.e., the target of treatment). If a lead is not correctly positioned, it is possible that the patient will receive little or no benefit from an implanted SCS system. Thus, correct lead placement can mean the difference between effective and ineffective pain therapy.
As such, the CP (described briefly above) may be used to instruct the neurostimulator to apply electrical stimulation to test placement of the leads and/or electrodes inter-operatively (i.e., in the context of an operating room (OR) mapping procedure), thereby assuring that the leads and/or electrodes are implanted in effective locations within the patient. The patient may provide verbal feedback regarding the presence of paresthesia over the pain area, and based on this feedback, the lead positions may be adjusted and re-anchored if necessary. Any incisions are then closed to fully implant the system.
Post-operatively (i.e., after the surgical procedure has been completed), a fitting procedure, which may be referred to as a navigation session, may be performed using the CP to program the RC, and if applicable the IPG, with a set of stimulation parameters that best addresses the painful site, thereby optimizing or re-optimizing the therapy. Thus, the navigation session may be used to pinpoint the stimulation region or areas correlating to the pain. Such programming ability is particularly advantageous after implantation should the leads gradually or unexpectedly move, which if uncorrected, would relocate the paresthesia away from the pain site.
Whether used inter-operatively or post-operatively, a computer program, such as Bionic Navigator®, available from Boston Scientific Neuromodulation Corporation, can be incorporated in the CP to provide a computer-guide programming system that facilitates selection of the stimulation parameters. The Bionic Navigator® is a software package that operates on a suitable computer and allows clinicians to program stimulation parameters into an external handheld programmer (referred to as a remote control). Each set of stimulation parameters, including fractionalized current distribution to the electrodes (as percentage cathodic current, percentage anodic current, or off), programmed by the Bionic Navigator® may be stored in both the Bionic Navigator® and the remote control and combined into a stimulation program that can then be used to stimulate multiple regions within the patient.
Prior to creating the stimulation programs, the Bionic Navigator® may be operated by a clinician in a “manual mode” to manually select the percentage cathodic current and percentage anodic current flowing through the electrodes based on a representation of the physical electrode arrangement displayed on the computer screen of the CP, or may be operated by the clinician in a “semi-automatic mode” to electrically “steer” the current along the implanted leads in real-time, thereby allowing the clinician to determine the most efficacious stimulation parameter sets that can then be stored and eventually combined into stimulation programs. In the navigation mode, the Bionic Navigator® can store selected fractionalized electrode configurations that can be displayed to the clinician as marks representing corresponding stimulation regions relative to the electrode array.
It may sometimes be desirable to estimate or predict the stimulation effects of electrical energy applied, or to be applied, to neural tissue adjacent to electrodes based on an estimation of the membrane response (e.g. transmembrane voltage potentials) of one or more neurons induced by the actually applied or potentially applied electrical energy. For example, given a specific set of stimulation parameters, it may be desired to predict a region of stimulation within the neural tissue of a patient based on an estimation of the neuronal response. As another example, when transitioning between electrode configurations, it may be desirable to adjust the intensity of the electrical stimulation energy based on an estimation of the transmembrane voltage potentials. Such a stimulation prediction software program can be incorporated into a CP to provide it with the capability of predicting a tissue region of stimulation to facilitate the determination of an optimum set of stimulation parameter and for actually stimulating the tissue region in accordance with the optimum stimulation parameter set.
Implantable lead positioning information is critical in SCS for both computer-guided programming systems and simulation/modeling systems.
For example, with respect to side-by-side electrode configurations, it is important that the CP, whether operated in a “manual mode” or “semi-automatic mode,” have knowledge of the lead stagger (i.e., the degree to which the first electrode of one lead is vertically offset from the first electrode of another lead) (or even lateral offset and/or angle of each lead relative to the midline of the spinal cord) either because the physician initially implanted the electrode leads in this manner to maximize the therapeutic effect of the stimulation or because the electrode leads subsequently migrated from an initially unstaggered configuration.
For example, if a representation of the relative positions of the leads is incorrectly displayed to the user during operation of the CP in the manual mode, it is possible that the electrode configurations selected by the user will be ineffective. Similarly, because the algorithm used to operate the CP in the semi-automatic mode relies heavily on the extent to which the leads are staggered, if the relative positions of the leads are improperly input into the CP, the current steering resulting from the semi-automatic mode may be ineffective.
Furthermore, it is also important that the CP have knowledge of the longitudinal position of the neurostimulation lead or leads relative to the vertebral segments, since it is known that the thickness of the cerebral spinal fluid (CSF) varies along the length of the spinal cord, with the thickness of the CSF increasing in the caudal direction. The neurostimulation lead(s) may be subjected to a different volume of CSF depending on their location relative to the longitudinal vertebral segments. As the CSF become thicker, it becomes more difficult to stimulate the spinal cord tissue without causing side-effects. As such, different electrode combinations may be appropriate for different lead implantation locations along the spinal cord.
The conventional manner in which lead positioning information is obtained is through fluoroscopy or static X-ray images, and in particular, reading the fluoroscopic or static X-ray images, identifying the location of the lead(s) relative to the segmental level, manually entering the data into the CP, and visualizing it with a predefined homogenous user interface (UI) model. In one example, with knowledge of the lead positioning information obtained from a medical image, such as an X-ray image, graphical leads representing the actual leads implanted within the patient are dragged and dropped on top of a homogenous spinal column model graphically displayed on the user interface, as described in U.S. patent application Ser. No. 13/104,826, entitled “System and Method for Defining Neurostimulation Lead Configuration,” which is expressly incorporated herein by reference.
Normally, the fluoroscopic or static X-ray images are translated into a very rough approximation of the actual location of the implanted neurostimulation lead(s) relative to the longitudinal vertebral segments (e.g., “around T7” or “between T7 and T8”). Furthermore, the manual process of inputting the lead position data into the CP could sometimes introduce errors; for example, the user may input incorrect lead position information (offsets, angles, etc.) by mistake, or precision error due to screen resolution as well as human eyes may limit the accuracy of the lead position information if using a drag-and-drop procedure. Inaccurate lead positioning could affect the output result of the computer-guided electrode programming algorithms that assume accurate electrode positions, resulting in a less therapeutic benefit. Furthermore, because the CP utilizes a homogenous anatomical model generated across a population that assumes that all patients have almost identical size of the spinal cord, computer-guided programming algorithms sometimes do not generate effective protocols due to the variation between individual patients.
Detecting lead positioning information directly from fluoroscopic or static X-ray images could provide more accurate information about an individual patient while also largely avoiding human-introduced errors. However, all currently available lead position detection techniques have limitations when used with computer-guided electrode programming algorithms in the context of post-op programming of the leads. In particular, those methods can only process post-operation imaging data, since it involves additional efforts, e.g., exporting image data, copying image data onto a USB drive, importing into commercial software on a separate computer, processing the images, identifying lead location, and then switching to a CP to manually enter lead information, which takes a relatively long time making it impossible to complete the whole process during or shortly after surgery.
There, thus, remains a need for a system or method that enables detecting and locating neurostimulation lead(s) relative to an anatomical structure, such as the spinal column, using medical images, such as fluoroscopic or static X-ray images, which would provide the possibility for real-time programming or simulation both in an intra-op and post-op environment.